Foundations of Gemstones: Gemmology for CAD/CAM Jewellers

From the deep red of a Burma ruby to the ocean-blue depths of a fine sapphire, gemstones transform simple metal settings into extraordinary pieces of jewellery. As a CAD/CAM jeweller, understanding the fundamentals of gemstones is not merely academic knowledge, it is essential for creating designs that are both beautiful and practical. In my years of teaching and writing about jewellery design, I have found that a thorough understanding of gemmology is what separates exceptional CAD/CAM jewellers from the rest.

Understanding Gemstone Properties for Digital Design

Gemstones are defined by three primary qualities: beauty, rarity, and durability. As digital designers, we must consider all three when creating settings in CAD software. Most gemstones are minerals with specific chemical compositions and crystalline structures, while others, like pearls and amber, come from biological sources.

The physical properties of gemstones directly influence our approach to design. Hardness, measured on the Mohs scale, indicates a stone’s resistance to scratching. Toughness, often confused with hardness, describes a stone’s ability to resist breaking or chipping. For instance, diamond sits at 10 on the Mohs scale, making it exceptionally hard, but its perfect cleavage planes can make it vulnerable to impact from certain angles.

In my book, The CAD/CAM Jeweller, I emphasise that understanding these properties is crucial when designing settings. For softer stones like opal or pearl (Mohs 5.5 to 6.5), I recommend creating protective settings that shield the stone from impacts. For harder stones like sapphire or diamond, more open settings can maximise light entry while maintaining security.

Optical Characteristics

A gemstone’s optical properties, how it interacts with light, create its distinctive beauty. When designing in CAD, we must consider properties like pleochroism (displaying different colours when viewed from various angles), lustre, and various interference effects such as adularescence in moonstone or the play of colour in opal.

For CAD/CAM jewellers, these optical properties should influence design decisions. For stones with strong pleochroism like tanzanite, I design settings that allow viewing from multiple angles to showcase colour variations. For gems with special optical effects like star sapphires, the setting must complement rather than obscure these unique features.

Practical Applications in CAD/CAM Jewellery Design

Facet alignment: In CAD, we can precisely align prongs or bezel edges with a stone’s facets, particularly effective for step-cut stones like emerald cuts

Size and weight: Factor in a gemstone’s specific gravity when designing pieces. Heavier stones like zircon may require additional support in the setting

Crystal habits: Use a gemstone’s natural crystal form as design inspiration. For example, design a setting for a hexagonal beryl crystal that echoes its six-sided form

Protecting vulnerable areas: For stones with perfect cleavage like topaz or kunzite, design settings that protect vulnerable areas. CAD allows precise positioning of protective elements like V-prongs or partial bezels

Conclusion

As CAD/CAM technology continues to advance, our ability to create innovative jewellery designs expands. However, the fundamental principles of gemmology remain constant. Understanding the physical properties, optical characteristics, and proper setting techniques for different gemstones is essential for creating jewellery that is not only visually stunning but also durable and practical.

In my experience training jewellers around the world, I have observed that those who combine technical CAD/CAM skills with a solid foundation in gemmology consistently produce the most remarkable work. The digital tools we use may change, but the gemstones we showcase have remained objects of fascination for millennia.